Patients who are immobilised due to partial or complete paralysis, or are recuperating from major surgery or otherwise bedridden for extended periods of time are often unable to exercise or move sufficiently under their own power. In many cases this is problematic and can lead to complications such as bed sores, and disuse atrophy of joints and soft tissues. Most solutions to this problem involve changing pressure points exerted on the patient's body by the bed or couch on which they are supported. Mattresses having fluidized beds incorporated into the structure or inflatable/deflatable devices are common but these units typically involve complicated mechanisms and circuitry and are quite expensive. A propagating wave through a mattress support is a desirable alternative to these other solutions.
Several types of wave generating devices have been patented. U.S. Pat. No. 3,981,612 issued to Bunger et al is directed to a wave generating apparatus which uses a set of rollers mounted on a carriage that is driven along a set of rails. A flexible sheet is secured at the ends of a frame and as the carriage is driven along the rails the roller displaces the sheet upwardly so that a wave motion is produced along the sheet. This device is quite bulky and is only able to produce one displacement wave for only one set of rollers.
U.S. Pat. No. 4,915,584 issued to Kashubara discloses a device for converting fluid flow into mechanical motion using an airfoil movable within a vertical track. As air flows over the air foil the foil moves vertically up or down in the vertical track thereby transmitting movement to a set of crank arms thereby rotating an axle which is attached at the ends to the two crank arms.
U.S. Pat. No. 4,465,941 issued to Wilson et al is directed to a water engine for converting water flow into other types of mechanical energy. Water flowing toward one side of the device engages a set of butterfly valves and a wheeled carriage is pushed along the frame of the barrage.
U.S. Pat. No. 3,620,651 issued to Hufton discloses a fluid flow apparatus that may operate as a pump or motor. The device includes several flexible sheets driven in oscillatory motion by a bulky crank assembly.
U.S. Pat. No. 4,999,861 issued to Huang describes a therapeutic bed with a wave surface generated through two longitudinal shafts, a multitude of offset cams and a support mechanism.
A PCT patent application PCT/EP98/01276 issued to Nestle S. A. uses a method similar to Huang's wave bed in a peristaltic pump. A longitudinal shaft drives a number of cams that sequentially compress a tube in a wavelike manner.
U.S. Pat. No. 5,267,364 issued to Volk also describes a wave bed activated through inflation and deflation of air pockets.
It would therefore be advantageous to provide a compact wave generating device that can be used for producing wave motion for use in chairs, beds or other therapeutic devices or alternatively may be adapted for converting wave motion into other types of mechanical or electrical energy.